First green grass of spring not enough to supply nutrient needs

COLUMBIA, Mo. – Turning cow herds out to graze pastures at the first sign of green grass harms forage growth later in the season. But there’s another big reason to wait, says a University of Missouri beef nutritionist.

Cows don’t benefit from early grazing as much as most herd owners believe.

Early grazing provides little quality and small quantity of grass, says Justin Sexten, Columbia. Herds need more nutrients than they get from early grass.

“Early pasture growth contains mostly water, only 25 percent dry matter,” Sexten warns. “Producers see this when they describe their cows as being ‘washy.’” Early grass has a high rate of passage through a cow’s digestive tract. In other words, don’t stand behind them.

After a hard winter, a cow nursing a calf needs extra feed until pastures are ready for grazing.

“With only 25 percent dry matter in the diet, a cow must eat 150 pounds of grass to meet her needs,” Sexten says.

A cow would walk constantly trying to find that much grass.

Quantity of growth at first green-up is minimal. “A cow can’t get a full mouthful of grass with each bite.”

The answer won’t appeal to farmers tired of winter feeding chores. Cows need continued feeding before grass grows large enough to supply nutrient needs. That means more hay and possible grain supplement.